This invention relates to eye-gaze tracking and, more particularly to an eye-gaze tracking device and method preferably for tracking the eye-gaze of a user on a surface such as a display.
Keyboards, mice or joysticks provide a communication interface between a human and an electronic device. Eye-gaze measurements have been used in physiological and psychological studies disclosed in document Arne John Glenstrup and Theo Engell-Nielsen: BS thesis, Laboratory of Psychology, University of Copenhagen which is available in Internet at the URL http://www.diku.dk/xcx9cpanic/eyegaze/article.html. Further eye-gaze tells about an interest area of an observer.
Present eye trackers are based on reflections of Infra Red (IR) light from the different layers of the eye, which is known as Purkinje reflections, and on reflection from a retina, which is seen as a bright iris. There are trackers that use only Purkinje images and trackers that combine the reflections from cornea and bright iris. Those reflections move with respect to each other and with respect to the bright iris depending on gaze direction. Usually one IR point source is enough but in order to increase accuracy several IR sources have been used. The retina has very large reflection at red and even more at IR wavelengths. Also the visibility of details, e.g. blood vessels, vanish when using longer wavelengths. Thus the retina looks very uniformly illuminated. This is why the iris-cornea method uses IR wavelengths.
Present eye trackers face major drawbacks to be able to fulfill the need for general usage. Eye trackers that are based on the Purkinje and/or the so called iris-cornea method must be calibrated frequently and a calibration is user dependent. In addition of that, these devices are not suitable for all people, because the eye structure of some people is incompatible for the device. This is because of physiological differences in the eye, especially physiological differences in eyelid positions. Other concerns are slowness of the device, that is, a delay in the existing devices prevents the required control.
An additional drawback is a general eye tracking structure of present eye trackers. Present eye trackers are bulky and heavy on a system level. These eye trackers require systems which are too massive for intelligent integrated electronic devices such as displays, virtual reality computer displays, portal computers and mobile phones.
Present eye-gaze tracking methods monitor the outer parts of an eye. These methods are very much person dependent and they are too much affected by personal eye geometry or the position of eyelids. Thus personal differences of eye physiology set a restriction for a common usage. These methods are inaccurate for required controlling and tracking.
A need for an improved user interface setting hands free is evident, as the devices become smaller, portable, more intelligent and ubiquitous. Eye-gaze tracking should set a data stream delivering high information content to the part of a display the eye is gazing. Efficient monitoring of eye-gaze is inevitable to eye-gaze controlled communication between a human and an electronic device. A control set could be defined by eye-gaze itself or eye-gaze combined to other existing control sets, such as a button. In addition, an eye-gaze tracking/control device should provide a response with an imperceptible delay for a device user for required usage. Current devices do not meet these abilities or they provide infeasible implementations.
The present invention provides a device and a method for tracking an eye-gaze on a surface such as a display of an electronic device and thus provides a base for controlling the electronic device according to the eye-gaze of a user.
According to a first aspect of the invention there is provided a method of tracking eye-gaze, the method comprising
emitting light having a certain wavelength;
transferring the light to the retina of an eye;
the wavelength of the light being such as to make the fovea of the eye resolvable;
detecting light that is reflected from said eye to form detection information including the resolvable fovea;
mapping the detection information to a predetermined surface, said surface being located at a distance from said eye, the location of the fovea on said surface forming an eye-gaze point.
According to a second aspect of the invention there is provided an eye-gaze tracking device, comprising:
a light source for emitting light having a certain wavelength;
means for transferring the light to the retina of an eye, the wavelength of the light being such as to make the fovea of the eye resolvable;
a detector for detecting light that is reflected from said eye to form detection information including the resolvable fovea;
a surface located at a distance from said eye; and
means for mapping the detection information to the surface for locating the fovea on said surface for forming an eye-gaze point by the location of the fovea.
In a preferred embodiment of the invention a deep blue or more preferably violet light source is used to emit light into the eye, particularly to the eye retina. Accordingly this means light having a wavelength in the range of about 395-500 nm, where a violet light having a wavelength of about 395-430 nm is preferred but blue light up to a wavelength of about 480 nm also works. Further an optical x-y matrix detector is used to measure the light reflected from eye retina. From the reflected light the foveal position, which is the eye-gaze, with respect to the optical assembly is measured with the detector.
According to another embodiment of the invention an eye-gaze tracker is integrated to a display, which can be a virtual reality display.
In one embodiment of the invention, eye-gaze control can set a data stream delivering high information content to the part of a display that the eye is gazing. Also in an embodiment, a control set or a control master is eye-gaze combined to hand controlling equipment. According to an embodiment of the invention, there may be provided software which measures and calculates fovea from data received from the detector, preferably the x-y detector, which may be a CCD (Charge Coupled Device) for example. In a further embodiment, the invention is provided with a pattern recognition calculation of blood vessels and comparing the calculations with a calibration pattern of blood vessels.
The invention provides several advantages over prior solutions. For example, a device according to one method of the invention may be implemented to be a simple light eye-gaze tracking device. This enables an embodiment for Virtual Reality (VR) displays having a reasonable physical size. Moreover, for portable computers or mobile units, such as mobile phones, a device for eye-gaze tracking according to the invention of reasonable structure can be implemented.
Preferably tracking and detecting the eye-gaze is based on the observation of the retina. This follows that the invention functions for different eyes although personal physical eye structure may vary considerably. This allows a large amount of users to apply the invention. The invention is thus suitable for substantially all users having normal physical human eye structure.
Moreover, the observation of the retina gives reliable and precise information of eye-gaze. Eye-gaze direction can preferably be determined without calibration of the device. Thus it is possible to obtain eye-gaze position on a display within immediate reaction from the eye-gaze device having measured with the detector (such as a CCD detector) and mapped to a display, e.g. a LCD.